This invention is concerned with the structural improvement of tear open convenience bottle caps formed out of lightweight sheet metal. One aspect of known tear open bottle caps, where the need for further refinement has become particularly apparent, concerns the easy removal of the cap from the underlying bottle lip or finish at the termination of the tearing action. Such removal, for optimum consumer acceptance, must be effected with minimal effort to avoid sloshing and spillage resulting from the instability of the bottle and its attached cap caused by the applied pressure to remove the cap from the bottle. Variations in tearing pattern as determined by existing score line configurations have not, as yet, completely fulfilled the above mentioned need in that the other basic strength requirements of the cap must still be met at the same time removal is being eased. Consequently, optimum positioning of the cap scoring must advantageously provide for adequate pressure retention as well as ease of tearing prior to cap removal and finally ease of cap removal from the bottle lip.
Heretofore, the common practice in making tear open container closures employing score lines to facilitate opening was to cover the scoring, if not completely then at least partially, with the closure gasket. The flowed-on type gasket most frequently used would then adhere to the interior surface of the closure at the score line area so that removal of the closure or cap requires tearing through the cured gasket. In the hand removal of lightweight metal convenience bottle caps, the tear factor at the score line is very important. Any added restraint, such as that imposed by tearing through the cap gasket, is quite significant and has a direct bearing on consumer acceptance of the closure. In addition, the use of high temperature resistant gasket compounds such as required for commonly employed sterilization food processing only further aggravates the problem with their commensurately greater resistance to tearing.